Sophia Perez is a high school student who works part time in a local sports equipment store. As part of her duties, she records daily transactions in a journal. One day she asks the owner, “You use the purchase invoice as your source document for recording purchases of merchandise on account. You use a memorandum as your source document for recording the entry when supplies are bought on account. Why don’t you use the invoice for both entries?” How would you respond to this question?